Smooth pursuit eye movements align the retina with moving targets, ideally stabilizing the retinal image. At a steadystate,
eye movements typically reach an approximately constant velocity which depends on, and is usually lower than the
target velocity. Experiment 1 investigated the effect of target size and velocity on smooth pursuit induced by realistic
images (color photographs of an apple and flower subtending 2° and 17°, respectively), in comparison with a small dot
subtending a fraction of a degree. The extended stimuli were found to enhance smooth pursuit gain. Experiment 2
examined the absolute velocity limit of smooth pursuit elicited by the small dot and the effect of the extended targets on
the velocity limit. The eye velocity for tracking the dot was found to be saturated at about 63 deg/sec while the saturation
velocity occurred at higher velocities for the extended images. The difference in gain due to target size was significant
between dot and the two extended stimuli, while no statistical difference exists between an apple and flower stimuli of
wider angular extent. Detailed knowledge of the smooth pursuit eye movements is important for several areas of
electronic imaging, in particular, assessing perceived motion blur of displayed objects.
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